#define _CRT_SECURE_NO_WARNINGS 1
#include"stdio.h"
//int Fib(int n)
//{
//	if (n <= 2)
//		return 1;
//	else
//		return Fib(n - 1) + Fib(n - 2);
//}
int Fib(int n)
{
	int a = 1;
	int b = 1;
	int c = 1;
	while (n>2)
	{
	    c = a + b;
		a = b;
		b = c;
		n--;
		
	}
	return c;

}
int main()
{
	int n = 0;
	scanf("%d", &n);
	int ret = Fib(n);
	printf("%d\n", ret);
	return 0;
}